Microbiology: Current Research

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Production, characterization and inhibition of fungal cellulases utilizing rice bran as substrate in solid state fermentation.

Loss of crops to fungal disease is increasing at an alarming rate throughout the world. Growing ecological hazards caused by chemical fungicides necessitate development of alternate pest management strategies in the form of botanical fungicide. Kaempferia angustifolia Rosc. (Zingiberaceae, commonly known as narrow-leaved peacock ginger) is a medicinally important herb with previously reported larvicidal activity. In this study, cellulase was investigated as a target for controlling spread of Fusarium oxysporum (a disease causing fungus in plants) using the aqueous leaf extract of narrow-leaved peacock ginger. Fungal culture of Neurospora crassa and F. oxysporum were used for cellulase production on a substrate of raw lignocellulosic material (rice bran) by solid state fermentation. N. crassa was kept as control. The optimum parameters for cellulase (FPase) production and characterization from the two fungi were found to be: N. crassa (incubation period: 2 d; optimum temperature: 70°C; pH optima: 6.0; optimum substrate: 100 mg of filter paper) and F. oxysporum (incubation period: 1 d; optimum temperature: 60°C; pH optima: 4.0; optimum substrate: 100 mg of filter paper). The study of cellulase inhibition was carried out by two methods: a) incubating the enzyme with serially diluted narrow-leaved peacock ginger leaf extract followed by enzyme assay, and b) incubating the substrate (filter paper) with different concentration of narrow-leaved peacock ginger leaf extract which was followed by addition of enzyme and cellulase assay. Both method of enzyme inhibition showed reduction in fungal cellulolysis. However, by using both methods, the percent reduction in cellulolysis was higher in F. oxysporum. The reduction in cellulolytic activity for F. oxysporum was 87.00% (first method) and 98.13% (second method) which revealed that second method of inhibition was markedly efficient compared to the first method. The decrease in cellulolytic activity for N. crassa of 40% (first method) and 85.45% (second method) was reported in this study. Thus, aqueous extract of narrow-leaved peacock ginger may be used as botanical fungicide to control plant pathogenic fungus (F. oxysporum) through reduced cellulolytic damage of different plant organs.